1. Field of the Invention
The present invention relates to a separator for a fuel cell and a method of manufacturing the separator. More specifically, in a fuel cell formed of a plurality of stacked unit cells, the present invention relates to a separator disposed between adjacent unit cells for forming a fuel gas passage and an oxide gas passage, by which fuel gas and oxide gas can be separated. The present invention further relates to a method of manufacturing the separator.
2. Description of the Related Art
As a method of a separator for a fuel cell, there is a known method described in Japanese Patent Application Laid-open No. HEI 8-222241 in which phenolic resin is added as a binder to carbon powder as a raw material for kneading and forming, which is baked for carbonization and graphitization. When the separator is manufactured in the aforementioned method, a block-shaped carbon member is prepared by the aforementioned baking step, the carbon member is machined and cut into a plate-like member such that a separator having a desired shape is obtained. As another method of manufacturing the separator, Japanese Patent Application Laid-open No. SHO 60-246568 discloses a method in which phenolic resin as a binder is mixed into carbon powder, and the mixture is subjected to a heat press forming at a temperature at which the resin is not graphitized. In the aforementioned method, the separator with a desired shape can be obtained by conducting the heat press process using a metal mold with a predetermined shape.
However, the former method includes the baking step for heating at a high temperature ranging from 1,000 to 3,000° C., and the step for machining the baked carbon. This may elongate the time required for manufacturing and further complicate the manufacturing process, resulting in increased manufacturing cost. Further, phenolic resin added to the carbon powder as the binder generates water during the baking step, which forms bubbles in the carbon members that have been baked. As a result, the gas-impermeability of the separator is deteriorated. In order to secure gas-impermeability of the separator, it is necessary to eliminate the bubbles generated in the carbon member. This may further complicate the manufacturing process.
Meanwhile the latter method does not include the baking step and the machining step, resulting in simplified manufacturing process compared with the former method. However in the heat press step, when the phenolic resin as a thermosetting resin is cured, the hydroxyl group contained therein reacts to generate gas (vapor). Accordingly bubbles are formed in the manufactured separator, resulting in insufficient gas-impermeability of the separator.